There are many types of conveyor belt scraper wherein one or several scraper blades are supported by a scraper apparatus to be urged against a belt to be scraped. Known apparatus may be broadly categorized as being of the counterbalance type, rotating spring type, and linear biassing type. The different types have relative advantages and disadvantages depending on environment in which they are to be used, material to be scraped, type of blade, width of belt, ease of maintenance and so on. This invention is concerned with apparatus of the last mentioned type.
Britz South African Pat. No. 81/7242 teaches a belt scraper including a housing with an elongate opening, an elongate scraper blade partly within the housing, and spring means in the housing acting on the blade to urge it outwardly from the housing against the belt to be scraped. The spring means comprises a plurality of coil springs, each of which is supported on an adjusting bolt that can be screwed into the housing in a direction parallel to the plane of the blade. The housing is formed in two separable parts to allow access to the interior of the housing for replacing the blade and cleaning purposes. In practice, this works satisfactorily, but has certain defects. For instance, adjusting the force which the coil springs urge the blade against the belt is cumbersome as each of the spring adjusting bolts has to be adjusted separately and may be dangerous if workmen have to work underneath the belt, especially when the belt is in use. The housing has to be separated to remove and replace a blade by loosening connecting bolts; this is time consuming. Also, dirt and water enter the housing which ultimately interferes with the free movement of the blade and causes rusting; this ingress of undesirable matter occurs even with the tolerances between the housing and blade being as small as possible within practical limits.
To overcome these defects the applicant proposed the invention disclosed in U.S. Ser. No. 157,732 filed Feb. 18, 1988 and now allowed, which teaches a scraper blade in a housing that is open in a direction away from a belt being cleaned, with the blade being biased by an elongate resilient strip passing along the length of the edge of the blade remote from its working edge. Means for tensioning and locking both ends of the tensioning strip is provided at each end of the belt scraper. This scraper satisfactorily overcomes the jamming, cleaning, replacement, retensioning, uniform tensioning and rusting problems and maintains tension over long periods and as the blade wears. However, while suitable for short blades, such as up to 1 or 1.5 meters, it has been found that it is difficult to obtain the required tension for longer blades.
This invention seeks to improve on the invention disclosed in the aforementioned U.S. application by providing a conveyor belt scraper that retains the benefits of the previous invention while being suitable for a full range of widths of conveyor belts and be capable of urging the blade against the belt with greater pressures when required.